Combination circuit breaker and dynamic unbalance switch for clothes washing machines



March 24, 1959 J, WORST 2,878,937

COMBINATION CIRCUIT BREAKER AND DYNAMIC UNBALANCE SWITCH FOR CLOTHES WASHING MACHINES Filed Sept. 19, 1955 INVENTOR. JOSEPH C. WORST HIS ATTORNEY United States Patent COMBINATION CIRCUIT BREAKER AND DY- NAMIC UNBALANCE SWITCH FOR CLOTHES WASHING MACHINES Joseph C. Worst, Louisville, Ky assignor to General Electric Company, a corporation of New York Application September 19, 1955, Serial No. 535,062

1 Claim. (Cl. 210-144) Another object is to provide an improved circuit ar- 1 rangement for clothes washing machines in which dual protection against electrical overload and against dynamic unbalance may be obtained from a single circuit breaker.

In carrying out my invention I provide a mechanical means mounted adjacent the spin basket and arranged to be actuated by the basket when it vibrates a predetermined amount. In turn, the mechanical means is -arranged to actuate a switch in a supplementary circuit coordinated with the electrical circuit of the driving motor of the machine. Actuation of the switch serves to cause tripping of the circuit breaker provided for overload protection, with the result that the same circuit breaker provides a dual protection for the machine opening the motor circuit both upon motor overload and upon excessive basket vibration.

Other features and advantages of my invention will be apparent in the following detailed description of the pres ently preferred construction shown in the accompanying drawings in which:

Fig. l is a vertical sectional elevation of a portion of a washing machine embodying my improved protective means;

Fig. 2 is a fragmentary sectional view showing an arrangement for mounting the mechanical actuating means and a switch included in the protective means; and

Fig. 3 is a circuit diagram showing the relation of the motor drive and the mechanically actuated switch.

Although my improved protective means may be adapted for use in rotating apparatus other than with washing machines, I have chosen to describe its operation with a domestic washing machine of well known type because in such service appreciable dynamic unbalance with resulting vibration may occur, particularly when the machine is placed upon an improper base or is carelessly loaded with heavy clothes.

Referring to the drawing, 1 indicates the outer casing, 2 the tub, and 3 the spin basket of a clothes washing machine. The tub 2. is suitably supported in the outer casing 1 and sealed to the cover thereof as indicated at 4. The spin basket 3 is mounted in the tub 2 for rotation about the vertical axis, and in the spin basket there is positioned a bladed agitator 5 which is oscillated to perform the washing operation as is well known. Water is supplied to the interior of the basket by any suitable means, not shown, and discharges into the tub through openings 6, as when the basket attains its discharge speed 2,878,937 Patented Mar. 24, 1959 during centrifugal extraction of water from wet clothes, or when an excess amount of water is supplied to a stationary basket.

Mechanism for efiecting oscillation of agitator 5 for clothes washing and rotation of basket 3 for centrifugal extraction is driven by a suitable electric motor 10 and is contained in a suitably mounted housing, not shown. Such mechanisms are well known and its specific structure forms no part of the present invention. One such suitable mechanism is disclosed in the patent to McNairy, No. 2,639,618, patented May 26, 1953, assigned to the same assignee as is the present invention.

An extension of easing 1 serves as a cover 7 for the washing machine and is provided centrally with a loading and unloading aperture into which a hinged lid 8. is adapted to fit. Upon the top of the cover a readily accessible panel support or backsplasher 9 is mounted, within which a portion of the machine protective means, including a circuit breaker 11 having a conductor 12 to a suitable power source, may be housed. This circuit breaker 11 serves as means for protecting the motor circuit upon the occurrence of an overload condition therein. Also, according to the present invention, it serves to terminate basket rotation when excessive vibration of the basket occurs as it rotates for centrifugal extraction. The means whereby the circuit breaker is controlled to perform this dual function are more fully explained hereinafter. The circuit breaker 11 may be of any suitable type but preferably will be of the bimetallic thermally-responsive type as shown diagrammatically in Fig. 3, that is, it will open when heated to a predetermined high temperature. In the illustrated embodiment a resistance heater 12a is connected serially with the bimetallic element 11 and enclosed in the same casing therewith to supply a portion of the heat for opening the circuit breaker upon either motor overload or excessive basket vibration. The bimetallic element 11 itself supplies the rest of the heat, being heated by the current flowing through it.

The circuit breaker preferably comprises a manually resettable device. That is, after having once opened, it remains open-until manually closed by the operator. In the illustrated circuit breaker the bimetallic element 11 comprises a disk which snaps from the full line position as shown in Fig. 2 to the dotted line position when heated to a predetermined temperature. In other words, it snaps from being concave in one direction to being concave in the other direction. Having snapped to the dotted line position, it then remains stressed in that position even after it cools down. In order for the bimetal to return to its full line, closed circuit position, a push button 11a must be manually-operated. The push button aetuates a -rod 11b which engages the bimetal adjacent its center and forces it to flex back to its closed circuit position. The rod 11b is normally biased out ofengagement with the bimetal by means of a suitable spring 110.

Connected to the circuit breaker 11 is a switch 13 which is mounted on a supporting member 20 positioned within casing 1 adjacent to and exteriorly of tub 2. The switch 13 is actuated in response to a predetermined vibration of the spinning basket and preferably is of the make-and-break type with two flexible contact arms 13a and 13b. The switch is connected on one side through conductors 14 and 14a to the power source. On its other side the switch is connected by a conductor to a current limiting resistor 15 and thence by conductor 16 to the circuit breaker 11. The switch 13 and resistor 15 thus in effect form a shunt circuit across the basket drive motor 10 which is also connected to the circuit breaker and conductor 14a. The motor 10 specifically is so connected by means of a suitable motor controller 17 (see Fig. 3).

Suitably positioned in the wall of the stationary tub 2 adjacent the member 20 is a flexible diaphragm or grommet 21 serving as a mounting for an elongated switch actuating arm 22. The arm 22 is adapted to pivot about a point intermediate its endsby flexing-the diaphragm. At .one end the arm is provided with a basket engaging projection or portion 23 and at its other end is provided with a switchengaging projection or portion23a. The two. projections of the arm may be mounted in spaced Planes in order to provide an elongated lever arrangement so. that the extent of movement of the basket contacting projection can produce a-multiplied extent of movement of the switch "contacting projection.

1 In order to prevent how ofcurrent: into the washing machine structure, projection 23a preferably is formed of dielectric material.

Itis preferred to mount the actuating arm so that projection 23 may contact basket 3 near its uppermost rim. Since the basket embodies a cantilever type mounting, its greatest gyratory deviation vor vibration from normal rotation occurs at the rim farthest from its drive mounting. Diaphragm 21 preferably is of a size and is formed of a flexible material, such as rubber, having a suitable period" of vibration and amplitude of movement. The switch actuating arm and the diaphragm are adapted to occupy a first position of rest, asindicated in Fig. 2 or a second position involving vibratory movement, as will now be described. When the gyrating basket strikes the projection 23, the arm 22 flexes the rubber diaphragm and pivots so as to force the projection 23a against the switch arm 13a and carry that arm into contact with the second switch arm 13b, thereby briefly closing the shunt circuit across the motor. 1

When the basket then moves awayfrom projection 23, the restoring action of the diaphragm-returns the arm 22 to itsnormal position. This withdraws projection 2311 from contact with the first switch contact arm 13a allowing it to break contact with arm 13b and open the switch again. However the switch is quickly re-closed if vibra-. tion of the basket continues. The basket'rimagain strikes projection 23 and the samesequence occurs; By repeated action of this sort the mechanical armrneans 22 repeatedly closesthe switch 13. 7 It will be understood that the arm is mounted so that this action takes place only when thevibration reaches a value deemed to require correction. A minor amount of unbalance may be tolerated, but when the mounting of the jmachine is improper, or when the distribution of heavy clothes in the basket is excessively unbalanced, continued use of themachine may result in excessive vibration and eventual damage, It is within this range of dynamic unbalance that my invention serves its best purpose and for which the particular setting of the mechanical actuating arm is selected.

The circuit breaker 11 as shown in Fig. 3, is connected so' that both the motor currentand the current drawn by switch 13 when closedpass through it.- Specifically the motor controller 17 and the switch 13' are connected in parallel paths which are energized "through the circuit breaker in series therewith. The switch 13 and its current limiting resistor, as mentioned above, form a shunt circuit around the motor.

The circuit breaker 11 provides overload protection for the motor in the conventional manner, opening quickly at large overloads and more slowly at smaller overloads. In a size of the illustrated machine suitable for domestic use, a type of drive motor may be advantageously employed which draws approximately 40 amperes under blocked rotor conditions. With such a motor the circuit breaker can be arranged to open after a predetermined interval, for example, one second, when the motor is drawing the blocked rotor current, and after longer intervals when the motor overload is smaller.

By this invention the circuit breaker 11 in addition to offering motor protection also serves as the meanswhereby the high speed rotation" of the basket is interrupted it excessive vibration occurs. This vibration, as explained above, results in the repeated, brief closing of the switch 13. The motor shunt circuit including switch 13 draws current through the circuit breaker whenever the switch is closed. Preferably the current limiting resistor 15 is so selected'thatthe shunt circuit draws approximately the blocked rotor current of the motor when the switch is closed. Drawing such a current the circuit would result in the circuit; breaker being opened after the predetermined interval selected for motor protection, for example one second, if the switch stayed closed that long. However, the actuating arm of the dynamic unbalance protective means will not continuously hold switch 13 closed for a second. The first time contact is made through the closed switch13 the bimetal in the circuit breaker will become heated, but not suificiently to trip the breaker. Thus unless vibration of the basket continues, the circuit breaker does not open. But if the vibration doescontinue, upon a suiiicient number of subsequent closings of--the switch 13 the bimetal will soon reach the requisite temperature needed to operate the breaker. Sincethe vibration of basket 4 is very rapid when a serious unbalance exists, the repeated contacts between projection 23 and the basket will quickly close the switch a sutficient number of times to actuate the circuit breaker; For example, in the illustrated machine it is contemplated-that the circuit breaker will be opened it the excessive vibration continues for only a few seconds. 2 t

- Once the circuit breaker is opened in response to the vibrationof thebasket, -'the main drive motor is deenergized. This causes the motor and the basket -to coast-'to a stop. Afterthe basket has stopped, the operatormay then -open' the lid 9 "and redistribute the clothes within. the basket. The operator can see where theclothes have collected unevenly -so as to unbalance the basket; andcan rearrange-them evenly so as to eliminate the unbalance.

Having distributed the clothes in this manner and closed the lid 8, the operator'then actuateethe push button 11a to close the cireuit break'er '11. The-bimetallic element has had time to coolwhile the clotheswere being arranged, whereby the =closing of-the"=circuit breaker is now possible. The closing of the circuit breaker energizes the motor again -so that-it drives the basket at centrifugalextraction or spin speed. Assumingthat the operator has properly distributed the clothes, the centrifugal extraction operation proceeds without further delay. However, the operator has" not distributed the clothes evenly'enough and 'exccssivevibration occurs, the switch 13 will be again closed repeatedly and actuate the circuit breaker 11 to de-energiz'e'the motor and terminate basket rotation. The operatorcan then distribute the clothes once-more to obtain a' betterbalance, and again close the circuit breaker: In-faet, the same sequence'will occur "the' 'operator'does distribute clothes evenly enough." Normally, 'however, a single rearrangement ofthe clothes will distribute. them evenly enough to avoid excessive vibration andopening of the circuit'breaker 11. It'will be noted that since the circuit breaker 11 must be manuallyclosed, there is no danger of the basket commencing-rotation while the operator still has her arm within the-basket.

It will be seen that by my invention I provide an improved control for washingmachines and the like, in which a single circuit interrupting device serves a dual function. Not only doesit provide motor overload pro tection, but also it serves as the meansfor interrupting basket rotation when excessive vibration occurs. The mechanical means for actuating the vibration sensing switch upon excessive vibration ofbasket, thereby to trip the circuit breaker, are simple and-inexpensive to fabricate and assemblewith the washing machine. Alsc; it will be, noted that in the illustrated means, no separate mechanical linkage is needed for resetting the actuating arm since the restoring action of the diaphragm in the tub wall normally brings the actuating arm back to a ready position for further operation.

With with regard to the circuit shown in Fig. 3, it will be understood that this is merely a simplified circuit for illustrating my invention. The elements of the conventional washing machine control circuits, not necessary to timer operated sequence control, solenoids for operating water valves and a motor for a drain pump, have not been shown in order to afford ease of understanding of the invention itself.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made; and I, therefore, contemplate by the appended claim to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters 29 Patent of the United States is:

In an automatic clothes washing machine: a rotatable basket subject to gyratory movement; a motor driving said basket, said motor drawing a predetermined current under locked rotor conditions; an overload circuit protector in the motor circuit effective to open said motor circuit upon motor overload conditions comprising a bimetallic element in series with said motor and a heating element adjacent said bimetallic element and in series therewith and with said motor, said bimetallic element opening said motor circuit when it reaches a predetermined temperature; a normally open shunt circuit across said motor in series with said overload protector; a current limiting resistor in said shunt circuit proportioned so as to draw approximately the same current as the motor under locked rotor conditions; a closing switch in said shunt circuit; and means responsive to basket vibration for repeatedly closing said switch upon the occurrence of excessive vibration to bypass said motor, energize said heater with the current drawn by said motor under locked rotor conditions through said shunt circuit, and cause said bimetallic element to open said motor circuit.

References Cited in the file of this patent UNITED STATES PATENTS 1,675,370 Miller July 3, 1928 1,803,203 Nelson Apr. 28, 1931 1,946,725 Andrews Feb. 13, 1934 FOREIGN PATENTS 598,739 Great Britain Feb. 25, 1948 

